We haven’t really talked about it much here, but I’ve been thinking about this concept more and more over the past few months. What if we looked at taking a route similar to this, as in doing something as simple as getting hundreds of thousands of plastic bottles (super cheap to manufacture… seriously, they are pennies a piece) and using them as a base, while growing salt-tolerent trees on top of them to bind the ags of bottles in place. Such a structure could be twice the length and width of the ClubStead, be right down near the waterline, and suffer less from the ups and downs associated with larger waves because the bags of plastic bottles and the trees would serve as shock absorbers, all at a fraction of the cost of significantly smaller concrete and steel structure.

Am I thinking to simplisticly here? Am I turning into a nut for even considering pursuing the research for this further?

What I meant to say was that the barrels will be submerged bottom up and a platform can be built on top. “Reverse” because it doesn’t displace water. The air inside the barrels will compress providing buoyancy.

… using [bottles] as a base, while growing salt-tolerent trees on top of them to bind the ags of bottles in place. Such a structure could be twice the length and width of the ClubStead, be right down near the waterline, and suffer less from the ups and downs associated with larger waves because the bags of plastic bottles and the trees would serve as shock absorbers, all at a fraction of the cost of significantly smaller concrete and steel structure…..

I don’t think this sort of structure would be a shock absorber in the way you mean it. The entire island, in large waves, would most likely roll with the water. If you’ve got trees and soil on top, it would be like a cross between a slow-motion, exagerated earthquake and land-waves. Hmm. I might even describe it as a gigantic waterbed. If it’s large enough, water might not get to far on top of it, but I don’t think there would be enough rigidity to help it ride the waves smoothly as a single entity.

It would be fine for small lakes or large rivers but not the open ocean. The great lakes develop large waves in storm conditions & smaller rivers seem more prone to drastic changes in water conditions in the rainy season.

What I meant to say was that the barrels will be submerged bottom up and a platform can be built on top. “Reverse” because it doesn’t displace water. The air inside the barrels will compress providing buoyancy.

I think it might be a bit too dangerous to merely have unsealed barrels upside down in the water. Technically, it would work, but there isn’t much of a safety factor. With turbulent water or titling the structure too far and the air would simply float out, leaving you with no more buoyancy. Also, even in a condition where the air compresses naturally, water must still be displaced in order for the weight of a floating structure to be supported by the water. I haven’t read through all these threads yet, so I don’t know if/why displacing water might be less than ideal.

I would propose that the same idea would work pretty well with sealed 50gallon drums in essentially the same way you describe. Banding the barrels together in honeycomb fashion and stacking them a few layers high would provide an easy way to build up some rigidity. In order to give them extra strength under the compressive forces of water at depth, you could pressurize them to match the depth you expect them to be used, allowing them a natural equilibruim with the water. As long as they are not punctured (which is really only a concern around the perimeter and underneath) you wouldn’t lose bouyancy, even if the entire structure were flipped completely over. This is an important safety factor, even when designing a structure that should be stable enough never to overturn like that.

Now, I had an idea along these lines earlier, which seems to fit in on this site. In fact, I believe my research into this concept is part of how I found this site. I designed a structure using 12 standard 40′ shipping containers as the floating base. I haven’t gotten as far as designing the above-surface structure, since I was merely researching potential cost and buoyancy issues. So far it looks promising, though. That much volume displacement can support quite a bit of weight. Unfortunately, I don’t have my buoyancy calculations with me and I don’t have time to do it all over.

I’ve heard a quoted estimate of between $2000-$3000 for a new shipping container. If you use $3500 to be conservative and to account for sealing, pressurizing, and connecting them, you’re starting at $42,000 just for the 8300 sq. ft. floating base “land” to build on. [roughly $23,000/acre] From there, you’d still need 65-75 vertical feet of supporting structure to get to where you need to build the living/working spaces, since I designed it at 50ft depth. So, from there, costs might tripple for the supports, then double the whole thing again for building the habitable space above that for a very crude estimate of $250,000-$300,000 for the whole thing…. crap. It doesn’t make sense. (If it’s too good to be true, it probably is.) $22/sq.ft. is unimaginably cheap… so lets say $250,000 just for an empty platform and minimal structure PLUS a more standard (though still cheap) $150/sq.ft. for the habitable space. [2.2million for 14,400sq.ft. + $300,000 for the base and you’re at $2.5 million for the whole thing.]

Eh. Quite a crude estimate and too many cost figures for such an early pre-design stage… but it seems reasonably competitive to land-based structures so far. I used 3 stories @ 4800sq.ft. for the above calculations, since it would be safest to keep the area of the above-surface structure narrower than the sub-surface supports for stability. At an additional cost of $62.5/sq.ft. of structure, it might be as reasonable starting point for a proof of concept platform option.

I was thinking something closer to the size of 55 gallon plastic drums, and they should be able to retain air for a substantial period of time. If/When they finally give, and I’m thinking it could be a decade or more into into the process, they will be so tightly intertwined with roots that it could be impossible to extract them. At that point, I think the buoyancy provided from the roots could counteract the loss of that from the barrel, so no divers would be needed.

Honestly, though, I’m moving away from the mangrove tree idea right now… I’m currently, squarely in the “knotted rope” camp. Please see my post in the VersaBuoy string for more info if you wish.